I can't help it, even though I'm the sort of person my mother told me not to play with.
Talking of not knowing arses from faces and going blind reminds me of the tale of the chap with the guide dog (seeing eye dogs, I think, in the US).
He's walking a new dog to the shops and stops at the kerb to wait for the dog to lead him across a gap in the traffic. Trouble is, the dog just looks up at him, cocks its leg and pisses down the man's trousers.
Solemnly the blind man delves into his pocket and brings out a biscuit. Stopping, he holds it out for the dog.
"Escuse me," says a bemused passer-by, "I don't know if you realise it, but your dog has just pissed down your leg. And yet you're giving it a biscuit; I don't understand."
"It's simple," says the blind man. "I'm giving him a biscuit to find out which end is his head. Then I'm going to shove my white stick up his arse!"